An exhaust gas recirculation (EGR) valve is typically used with automotive internal combustion engines to meter exhaust gas from a source such as the exhaust manifold to the intake manifold where the exhaust gas is introduced to the combustion air charge to assist in the reduction of regulated exhaust constituents. The harsh underhood environment of an automobile exposes the EGR valve to high temperatures both from the internal flow of exhaust gas and external engine temperatures. Additionally, high levels of vibration, dirt and moisture require an EGR assembly which is immune to contamination from external as well as internal sources.
Electromagnetic solenoid actuators used in state-of-the-art exhaust gas recirculation valves can be sensitive to high temperatures which are transferred from the exhaust gas passing through the valve. Attempts to isolate the actuators have resulted in contamination concerns, especially in the area of valve stem entry to the actuator housing. Actuator mounting to the valve base presents a challenge due to the high vibrational loads experienced by the mounting hardware and associated durability concerns.
In certain sealed actuator housings, exhaust gas enters the actuator because the actuator resides at intake manifold pressure (vacuum) in the valve-closed mode. During closed-open valve transitions, exhaust is drawn into the actuator by the vacuum condition until an equilibrium condition exists. As a result, hot moisture-laden exhaust gas may be drawn into the actuator housing to condense on the lower temperature solenoid assembly causing a potential for corrosion.